Article Title: Altered Microhabitat Use and Movement of Littorinid Gastropods: the Effects

Article title: Altered microhabitat use and movement of littorinid gastropods: the effects of parasites

Journal: Marine Biology

Authors:K. O’Dwyer1)*, T. Kamiya1) & R. Poulin1)

1) Evolutionary and Ecological Parasitology Group, Department of Zoology, University of Otago, P.O. Box 56, Dunedin 9054, New Zealand.

Corresponding author:

Figure S1. Barplots of mean snail density (m-2) for each species, Austrolittorina antipodum and A. cincta, at differing heights within littorinid zone and in each of three microhabitats (rock surface, crevice, rock pool). Standard error bars shown

Figure S2. Forest plot showing MCMC posterior mean estimates for difference in crevice and rock surface microhabitat use between infected and uninfected littorinids, with 95% credible intervals (CIs). Black and grey lines represent Austrolittorina antipodum and A. cincta, respectively. Differences where CIs do not cross zero are considered significant. A negative value indicates greater use of crevices by infected snails, while a positive value indicates greater use of the rock surface by infected snails.Sample sizes (N) shown are total number of possible datapoints for A. antipodum and A. cincta, respectively

Figure S3. Forest plot showing MCMC posterior mean estimates for difference in distance moved from original release site between infected and uninfected littorinids, with 95% credible intervals (CIs). Black and grey lines represent Austrolittorina antipodum and A. cincta, respectively. Differences where CIs do not cross zero are considered significant. A negative value indicates a shorter distance travelled by infected snails, while a positive value indicates greater distance travelledby infected snails.Sample sizes (N) shown are total number of possible datapoints for A. antipodum and A. cincta, respectively

Figure S4. Forest plot showing MCMC posterior mean estimates for the difference in vertical distance travelled between infected and uninfected littorinids, with 95% credible intervals (CIs). Black and grey lines represent Austrolittorina antipodum and A. cincta, respectively. Differences where CIs do not cross zero are considered significant. A negative value indicates greater downward movement by infected snails, while a positive value indicates greater upwards movementby infected snails.Sample sizes (N) shown are total number of possible datapoints for A. antipodum and A. cincta, respectively

Table S1. Percentage of missing data for each dataset used in each model

Model / Percentage missing data
Austrolittorina antipodum
24-h study / 14.3
Weekly study / 24.3
Monthly study / 37.1
Lab study / 0
Austrolittorina cincta
24-h study / 3.3
Weekly study / 23.7
Monthly study / 46.7
Lab study / 0

Table S2. MCMCglmm models for difference inuse of rock surface or crevices, between infected and uninfected littorinid species, (a) Austrolittorina antipodum and (b) Austrolittorina cincta. Separate models were employed for 24-h, weekly, monthly and lab studies. Repeated measures of individuals over time were accounted for by including snail identity as a random effect. Tag colour refers to colour of tag attached to snails, snail identity is denoted as SnailID and tank identity as TankID, Origin is the original microhabitat the littorinid was collected from; all were included as random effects. Any case where credible interval (CI) does not cross zero indicates a significant result and can be seen in bold. All values have been c2 corrected

Model / Variable / Posterior mean / Posterior mode / CI - L / CI - H / Varianceposterior means / Iterations, thinning, burnin
(a)
24-h study
Intercept / -1.7859 / -1.8838 / -8.4453 / 3.8738 / Tag colour=4.0298 / 15x106, 1x103, 1x 107
Status / 0.3104 / 0.1553 / -1.0353 / 1.6953 / Origin=59.4171
Length / 0.7891 / 0.7411 / 0.1841 / 1.4103
Weekly study
Intercept / -1.2089 / -1.0850 / -2.4161 / 0.4710 / Tag colour=0.1602 / 15x106, 1x103, 1x 107
Status / 0.5516 / 0.5574 / 0.0309 / 1.0942 / SnailID=0.4544
Length / 0.4667 / 0.5022 / 0.2622 / 0.6986 / Origin=10.7921
Monthly study
Intercept / -0.3821 / -0.2896 / -6.8821 / 5.2463 / Tag colour=1.9395 / 15x106, 3x103, 1x 107
Status / 1.5119 / 1.0981 / -0.2526 / 3.9170 / SnailID=7.5364
Length / 0.3488 / 0.2352 / -0.4007 / 1.3079 / Origin=39.3154
Lab study
Intercept / 6.4287 / 5.6892 / 2.4067 / 10.9792 / Nested SnailID in / 2x107, 6x103, 5x105a
Status / 1.3783 / 0.9869 / -2.5618 / 5.8400 / TankID=19.8603
Length / -1.3473 / -1.4940 / -3.5592 / 0.9232
(b)
24-h study
Intercept / -2.0739 / -1.3914 / -10.1302 / 4.5898 / Tag colour=32.7298 / 5x107, 5x103, 1x107
Status / 0.2360 / 0.3051 / -1.6467 / 2.1823 / Origin=42.7203
Length / -0.0642 / -0.0617 / -0.8491 / 0.7062
Weekly study
Intercept / -0.4831 / -0.6283 / -3.8468 / 3.8777 / Tag colour=5.6391 / 15x106, 1x103, 1x 107
Status / 0.3280 / 0.2229 / -0.3807 / 1.0102 / SnailID=0.3205
Length / 0.0945 / 0.1154 / -0.2520 / 0.3811 / Origin=25.5063
Monthly study
Intercept / -3.4158 / -1.6628 / -19.7584 / 9.5750 / Tag colour=25.5322 / 5x107, 5x103, 1x107
Status / 4.7539 / 3.1034 / -0.0087 / 12.3398 / SnailID=17.3519
Length / 0.6387 / 0.5122 / -1.4614 / 3.3331 / Origin=171.1052
Lab study
Intercept / 2.8965 / 1.6709 / -1.8783 / 8.1281 / Nested SnailID in / 2x107, 6x103, 5x105a
Status / 4.3096 / 5.0075 / -0.9185 / 8.9441 / TankID=73.0538
Length / -0.8394 / -0.7064 / -2.5777 / 0.8562

a indicates a model which still contained slight autocorrelation between lags in the MCMC chains for one random effect (<0.41).

Table S3. MCMCglmm models for difference in total distance travelled, between infected and uninfected littorinid species, (a) Austrolittorina antipodum and (b) Austrolittorina cincta. Separate models were employed for 24-h, weekly, monthly and lab studies. Repeated measures of individuals over time were accounted for by including snail identity as a random effect. Units refers to residual variance of fixed effects. Tag colour refers to colour of tag attached to snails, snail identity is denoted as SnailID and tank identity as TankID; all were included as random effects. Any case where credible interval (CI) does not cross zero indicates a significant result and can be seen in bold

Model / Variable / Posterior mean / Posterior mode / CI - L / CI - H / Variance posterior means / Specifications
(a)
24-h study
Intercept / 3.1679 / 3.0986 / 2.3548 / 3.9487 / Units=4.6140 / All models
Status / -0.6115 / -0.8268 / -1.6562 / 0.5098 / Tag colour=0.0399 / 4x106, 2x103, 4x105
Length / 0.5004 / 0.4742 / 0.1349 / 0.8692
Weekly study
Intercept / 5.0497 / 5.1024 / 4.5183 / 5.5442 / Units=6.0040
Status / -1.5520 / -1.6206 / -2.2803 / -0.7959 / Tag colour=0.0129
Length / 0.6188 / 0.5780 / 0.3679 / 0.8808 / SnailID=1.5000
Monthly study
Intercept / 6.8310 / 6.8278 / 6.0415 / 7.7595 / Units=8.0050
Status / -1.9145 / -1.8802 / -3.2005 / -0.8307 / Tag colour=0.0302
Length / 0.7206 / 0.7851 / 0.2796 / 1.1091 / SnailID=0.0732
Lab study
Intercept / 1.8663 / 1.78243 / 1.4509 / 2.3339 / Units=2.4660
Status / -0.2904 / -0.2262 / -0.8580 / 0.3596 / Nested SnailID in
Length / 0.1402 / 0.1494 / -0.1746 / 0.4728 / TankID =0.0023
(b)
24-h study
Intercept / 5.94869 / 5.9842 / 4.3580 / 7.7200 / Units=7.919
Status / -1.42597 / -1.5712 / -3.3974 / 0.5888 / Tag colour=2.272
Length / 0.54612 / 0.4869 / -0.0947 / 1.2280
Weekly study
Intercept / 6.5874 / 6.5198 / 5.5330 / 7.6213 / Units=9.4880
Status / -0.4863 / -0.5691 / -1.9973 / 0.9954 / Tag colour=0.0287
Length / 0.1570 / 0.1619 / -0.2904 / 0.6239 / SnailID=2.7980
Monthly study
Intercept / 8.0863 / 8.0045 / 6.2663 / 9.8725 / Units=11.4200
Status / 0.5313 / 0.9233 / -1.7043 / 3.1834 / Tag colour=0.3475
Length / 0.7545 / 0.6354 / -0.2334 / 1.7803 / SnailID=0.2892
Lab study
Intercept / 1.75760 / 1.7167 / 1.0551 / 2.4011 / Units=3.4990
Status / 0.09676 / 0.1608 / -0.6741 / 0.9101 / Nested SnailID in
Length / -0.03842 / -0.0699 / -0.2447 / 0.1591 / TankID =0.0035

Table S4. MCMCglmm models for difference in vertical distance travelled, between infected and uninfected littorinid species, (a) Austrolittorina antipodum and (b) Austrolittorina cincta. Separate models were employed for 24-h, weekly, monthly and lab studies. Repeated measures of individuals over time were accounted for by including snail identity as a random effect. Units refers to residual variance of fixed effects. Tag colour refers to colour of tag attached to snails, snail identity is denoted as SnailID and tank identity as TankID; all were included as random effects. Any case where credible interval (CI) does not cross zero indicates a significant result and can be seen in bold

Model / Variable / Posterior mean / Posterior mode / CI - L / CI - H / Variance posterior means / Specifications
(a)
24-h study
Intercept / -3.7656 / -4.4114 / -7.9970 / 0.4972 / Units= 142.2000 / 4x106, 2x103, 4x105
Status / 1.1075 / 2.0643 / -5.2051 / 6.6967 / Tag colour=0.4209
Length / -1.9650 / -1.9745 / -3.9921 / 0.1690
Weekly study
Intercept / -11.7894 / -11.4171 / -16.3355 / -7.2755 / Units=244.9000 / 4x106, 2x103, 4x105
Status / 6.1990 / 4.9976 / -0.0054 / 11.6888 / Tag colour=0.4174
Length / -4.9278 / -5.2174 / -6.9526 / -2.9136 / SnailID=120.0000
Monthly study
Intercept / -7.6030 / -6.9452 / -15.8677 / 0.0451 / Units=251.6000 / 5x107, 5x103, 1x106a
Status / -2.1836 / -2.2917 / -12.0713 / 8.5225 / Tag colour=11.8800
Length / -5.7174 / -5.7994 / -9.2317 / -2.2040 / SnailID=211.5000
Lab study
Intercept / 1.5873 / 1.5213 / 0.4765 / 2.6288 / Units=14.9700 / 4x106, 2x103, 4x105
Status / -0.3329 / -0.1566 / -1.8036 / 1.1623 / Nested SnailID in
Length / -0.2126 / -0.4030 / -1.0252 / 0.5355 / TankID=0.0267
(b)
24-h study
Intercept / -33.4936 / -33.1645 / -48.5892 / -18.2194 / Units=571.2000 / 4x106, 2x103, 4x105
Status / 19.4025 / 18.4133 / 1.2593 / 35.9130 / Tag colour=126.7000
Length / -6.2185 / -5.2679 / -11.8971 / -0.2528
Weekly study
Intercept / -3.5487 / -4.0596 / -11.7248 / 4.8483 / Units=452.5000 / 4x106, 2x103, 4x105
Status / 0.5179 / 0.0776 / -11.8407 / 12.2419 / Tag colour=9.4810
Length / -0.5317 / -0.5090 / -4.2403 / 3.1477 / SnailID=200.3000
Monthly study
Intercept / 23.163 / 22.9466 / 10.693 / 34.570 / Units=446.4000 / 1x107, 5x103, 4x105
Status / -8.333 / -9.7830 / -24.145 / 7.612 / Tag colour=13.7400
Length / 1.030 / 1.3489 / -5.427 / 6.918 / SnailID=45.9000
Lab study
Intercept / 1.0164 / 1.0672 / 0.0076 / 1.9760 / Units=8.0390 / 8x106, 3x103, 4x105
Status / -0.4945 / -0.4235 / -1.6425 / 0.7248 / Nested SnailID in
Length / 0.0049 / -0.04783 / -0.3020 / 0.3142 / TankID=0.0112

a indicates a model which still contained slight autocorrelation between lags in the MCMC chains for one random effect (<0.31).